Help: I love M43 but on the edge

Pretty awesome feedback; a big thank you to all who spent time replying.

Renting FF equipment is good piece of advice; I am going to try that in couple of weeks. Thank you!

Olympus bodies with IBIS is very good suggestion too. Going to try that as well with existing gear. I have lots of legacy gear so IBIS is hopefully going to make a big difference. I completely forgot how awesome my C-2100 Zoom was that is still sitting there in closet from 1998 Thank you again for reminding me about Olympus.

For the rest I felt I should have included more details.

When I said indoor pictures I should have been specific that I shoot sports and trade shows/exhibitions. So I am always in a big hall/gymnasium standing somewhere in the back (cannot afford to be on the front you know). So I am am always looking for reach and speed. My 35-100mm/F2.5 is doing just okay here. Bumping up ISO beyond 800 creates too much noise imo. Wish there was a fast 100-300mm available for MFTs that way I could live with 5 lenses maybe (12-35mm/F2.5, 35-100mm/F2.5, 100-300mm, 25mm/F1.4 and Oly 75mm/F1.8). Long/Fast tele is unfortunately not there.

When I said birds I meant BIF. Should have been clear about that. Sorry. GH4 has awesome burst rate but AF-C is not that great imo (plus burst rate drops significantly when shooting in RAW and the buffer fills up quickly - camera takes for ever to comeback to life on my U3 card)

Regarding Bokeh/DoF it is matter of personal taste ... I personally like pictures with backgrounds completely washed out. There is no such lens in MFT ecosystem imo that can do it for me no matter how I positions himself. Some legacy glass comes close and sample pictures I have seen from Olympus 75mm seem like it might be a possibility .. good suggestion from my friends here that I have quite a bit of collection why not buy couple missing primes to see if I can get what I am looking for. Going to try that too.

Again, thank you all. I have got lot of information. Going to try proposed solutions/techniques. Hope it gets better. You made me feel comfortable ... well, for now at least .. till I attend another exhibition ... cheers!

This thread has grown too long imo. If moderators prefer they can close it now. It has solved the purpose for me. Thank you!